The present invention relates generally to prosthetic devices and, more particularly, to a valve assembly for use with a prosthetic limb socket.
A prosthesis is often used to replace an amputated portion of a limb and to help restore the amputee's ability to use that limb. A prosthesis for a lower extremity amputation will often include an artificial foot connected to an upright assembly (pylon, tube or shaft) which is in turn connected to a custom fitted socket assembly.
Prior art prosthetic assemblies generally require an inner liner or sheath generally comprising a flexible, thermoplastic material conforming to the residual limb of the amputee, and a more rigid, thermoplastic outer socket which is attached to the upright assembly of the prosthetic assembly. The outer socket may or may not be used with the inner liner or sheath. The inner liner or sheath, when used, is usually donned by inverting and rolling it onto the residual limb. When used, the inner liner or sheath is typically designed to interface with and cushion the amputee's residual limb, to protect the amputee's residual limb from the interconnecting components which attach the outer socket to the upright assembly, and to provide an air-tight seal between the residual limb and the outer socket. The typical prior art prosthetic assembly included a relief valve mounted in the outer socket for the expulsion of air within the socket as it was donned. This type of prosthesis is typically held to the residual limb of the patient by suction formed between the inner liner or sheath or residual limb and the outer socket. To further maintain suction within the socket, a suspension sleeve is worn over the upper end of the socket and over the adjacent residual limb. Such suspension sleeves also hold the socket onto the residual limb.
One of the limitations encountered with this type of prosthetic assembly is that the weight of the prosthesis is carried mostly by the distal part of the residual limb. Another limitation is due to the location of the relief valve not being at the most distal point of the socket. As the residual limb with or without a liner or sheath is extended within the socket past the valve, the valve becomes blocked by the residual limb and thus fails to expel all of the air from within the socket.
Throughout the development of these type of prostheses, it was found that total contact was essential between the residual limb and the socket to attain an even weight distribution of the patient and to distribute the suspension of the prosthesis over the whole surface of the residual limb.
Furthermore, it is well known that when an amputee dons a prosthesis and begins taking the pressures of transmitting the weight of the body through the surface area of the residual limb to the bone, there is increased pressure on the residual limb which causes the eventual loss of fluids within the residual limb. This loss of fluids causes the volume of the residual limb to decrease during the day. It varies from amputee to amputee, but it is a constant among all amputees and the more “fleshy” and the softer the residual limb, the more volume fluctuation there will be. The greater the weight and the smaller the surface area, the greater the pressures will be and the more “swings” there will be in fluids. In the past, the amputee had to compensate for this volume decrease by removing the artificial limb and donning additional stump socks to make up for the decreased residual limb volume. The volumetric dimensions of the residual limb will change within a very short period of time due to fluid retention or fluid loss.
Because of such pressures on the residual limb resulting in volume changes thereof, pistoning during ambulation of the residual limb within the socket occurs since the prosthesis does not fit well at all times.
One typical system designed to create such suction and compensate for varying residual limb volume is disclosed in U.S. Pat. No. 6,761,742 to Caspers. The Caspers patent discloses various embodiments of suction systems associated with the type of prosthesis discussed above. In one embodiment, Caspers discloses a vacuum pump attached to the upright assembly which includes a mechanical or motor-driven pump. The pump is fluidically connected to the interface between the liner and socket via conduits, thus creating a vacuum within the prosthetic socket to draw the liner into close contact with the socket. In another embodiment, Caspers discloses a weight-actuated vacuum pump mechanically actuated by downward force exerted on the pump during ambulation of the amputee. This pump is also mounted in the upright assembly and is fluidically connected to the interface between the liner and socket via a passageway extending through the upright assembly itself.
Another typical system is disclosed in U.S. Pat. No. 6,287,345 to Slemker et al. which includes a prosthetic socket having a distal extension. Mounted within the distal extension is a valving system for relieving air from within the socket as the amputee donns the prosthesis socket. Although this valving system operates efficiently, the manufacture and assembly thereof is quite complicated since it includes several intricately molded parts some of which are made of metal. Furthermore, the valving system is attached to the prosthetic socket with screws.
Thus, from the above examples of the prior art systems, some of the drawbacks are noise and weight related to the use of metal components in the pump body, packaging limitations due to the geometry of the pumps, which affect the cosmetic appearance of the prosthesis, the need for batteries or other power sources, and the need for pistons and cylinders to pump air out of the socket.
The present invention is a novel and unique design to overcome all the limitations highlighted above of the current prior art systems.